{
 "cells": [
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "# Python Cheat Sheet\n",
    "\n",
    "Basic cheatsheet for Python mostly based on the book written by Al Sweigart, [Automate the Boring Stuff with Python](https://automatetheboringstuff.com/) under the [Creative Commons license](https://creativecommons.org/licenses/by-nc-sa/3.0/) and many other sources.\n",
    "\n",
    "## Read It\n",
    "\n",
    "- [Website](https://www.pythoncheatsheet.org)\n",
    "- [Github](https://github.com/wilfredinni/python-cheatsheet)\n",
    "- [PDF](https://github.com/wilfredinni/Python-cheatsheet/raw/master/python_cheat_sheet.pdf)\n",
    "- [Jupyter Notebook](https://mybinder.org/v2/gh/wilfredinni/python-cheatsheet/master?filepath=jupyter_notebooks)\n",
    "\n",
    "## `__main__` Top-level script environment\n",
    "\n",
    "`__main__` is the name of the scope in which top-level code executes.\n",
    "A module’s **name** is set equal to `__main__` when read from standard input, a script, or from an interactive prompt.\n",
    "\n",
    "A module can discover whether or not it is running in the main scope by checking its own `__name__`, which allows a common idiom for conditionally executing code in a module when it is run as a script or with `python -m` but not when it is imported:"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "if __name__ == \"__main__\":\n",
    "    # execute only if run as a script\n",
    "    main()"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "For a package, the same effect can be achieved by including a **main**.py module, the contents of which will be executed when the module is run with -m.\n",
    "\n",
    "For example we are developing script which is designed to be used as module, we should do:"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "# Python program to execute function directly\n",
    "def add(a, b):\n",
    "    return a+b\n",
    "\n",
    "add(10, 20) # we can test it by calling the function save it as calculate.py"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "# Now if we want to use that module by importing we have to comment out our call,\n",
    "# Instead we can write like this in calculate.py\n",
    "if __name__ == \"__main__\":\n",
    "    add(3, 5)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "import calculate\n",
    "\n",
    "calculate.add(3, 5)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "### Advantages\n",
    "\n",
    "1. Every Python module has it’s `__name__` defined and if this is `__main__`, it implies that the module is being run standalone by the user and we can do corresponding appropriate actions.\n",
    "2. If you import this script as a module in another script, the **name** is set to the name of the script/module.\n",
    "3. Python files can act as either reusable modules, or as standalone programs.\n",
    "4. if `__name__ == “main”:` is used to execute some code only if the file was run directly, and not imported."
   ]
  }
 ],
 "metadata": {
  "kernelspec": {
   "display_name": "Python 3",
   "language": "python",
   "name": "python3"
  },
  "language_info": {
   "codemirror_mode": {
    "name": "ipython",
    "version": 3
   },
   "file_extension": ".py",
   "mimetype": "text/x-python",
   "name": "python",
   "nbconvert_exporter": "python",
   "pygments_lexer": "ipython3",
   "version": "3.7.0"
  }
 },
 "nbformat": 4,
 "nbformat_minor": 2
}
